I think there needs to be a balance. I get so interested in worlds of games like Skyrim that I lose interest. OoT had a nice balance, but I'd like it to be a LITTLE more to explore. There needs to be a balance between letting the players explore, and providing the player with obstacles that create that sense that they're MISSING out on MORE if they don't progress in the story. They WANT to see what's behind that big pile of rocks, or across that gap... but they can't... YET. Then they get excited when they finally can and immediately go back.
In the Elder Scroll games there are no obstacles... I can explore everything. Which is cool... but I eventually just get bored because nothing draws my interest back.